The present specification relates generally to fabrication processes for integrated circuits (IC). More specifically, the present specification relates to an improved system for and method of developing a photoresist layer on a semiconductor substrate.
The semiconductor industries continue to manufacture semiconductor integrated circuits with higher and higher densities on a smaller chip area. The desire for large scale integration has led to a continued shrinking of the circuit dimensions and features of the devices so as to reduce manufacturing costs and to improve circuit functionality. The ability to reduce the size of structures such as gate lengths in field-effect transistors is driven by lithographic technology which is, in turn, dependent upon the wavelength of light used to expose the photoresist. In current IC fabrication processes, optical devices expose the photoresist to light having a wavelength of 248 nm (nanometers). Research and development laboratories are experimenting with light having a wavelength of 193 nm. Further, the next generation lithographic technologies will in all likelihood progress toward a radiation having a wavelength of 157 nm and even shorter wavelengths, such as those used in Extreme Ultra-Violet (EUV) lithography (e.g., 13 nm).
In a conventional lithographic process, after a semiconductor wafer is coated with photoresist and exposed to light with a circuit pattern, developer is applied to the photoresist to remove portions of the photoresist. The developer is removed with a water rinse and dried by a spinning process before subsequent etching.
One obstacle to the further reduction in printed feature size is the pattern collapse between photoresist lines or other photoresist features caused by the water rinse and drying step. FIGS. 1 and 2 illustrate the problems caused by this conventional technique. In FIG. 1, a wafer 10 is shown having photoresist lines 12. Rinse water 14 is illustrated after the rinsing step and just prior to drying. The inherent cohesive and adhesive forces of water create surface tension between photoresist lines 12 as the water evaporates. During the drying step, as shown in FIG. 2, fine photoresist lines 12 are pulled laterally by the surface tension, causing pattern collapse and ruining the resulting etch.
Currently, pattern collapse is avoided by limiting the printed feature size. One proposed solution is to freeze-dry a rinse liquid (i.e., tert-butanol). However, this method is time consuming, resulting in decreased throughput. Although the method could be done in batch processing, this adds complexity to the process. Another proposed solution is to use perfluorohexane as a rinser. However, perfluorohexane is difficult to dispose of. If pattern collapse can be reduced or eliminated, narrower features can be printed, thereby enabling higher microprocessor speeds and higher device density on the substrate.
Accordingly, there is a need for an improved system for and method of developing a photoresist layer. Further, there is a need for a system for and method of developing a photoresist layer to reduce or eliminate pattern collapse. Further still, there is a need for a system for and method of reducing surface tension caused by the water rinse during photoresist development. The teachings hereinbelow extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the above-mentioned needs.
According to an exemplary embodiment, a method of developing a photoresist layer on a semiconductor wafer in a developing chamber includes applying a developer to the photoresist layer, applying an evaporating solution to the photoresist layer, and drying the photoresist layer.
According to another exemplary embodiment, a method of patterning a photoresist layer on a semiconductor wafer includes exposing the photoresist layer to light, developing portions of the photoresist layer with a photoresist developer, whereby photoresist lines remain on the wafer, rinsing the developed portions of the photoresist layer with an alcohol rinse, and drying the wafer.
According to yet another exemplary embodiment, an integrated circuit on a semiconductor substrate includes devices fabricated by a photolithographic process including the steps of: applying a photoresist layer to the semiconductor substrate; exposing the photoresist layer to light; developing portions of the photoresist layer with a photoresist developer, whereby photoresist lines remain on the wafer, rinsing the developed portions of the photoresist layer with an alcohol rinse, and drying the wafer.